Ch7-Analyzing Ethernet LAN Switching

Question 1

An Ethernet frame sent to destination address FFFF.FFFF.FFFF, meaning that the frame should be sent to all hosts on that LAN

Answer 1

broadcast frame

Question 2

An Ethernet frame whose destination MAC address is listed in a switch’s MAC address-table, so the switch will forward the frame out the one port associated with that entry in the MAC address-table

Answer 2

known unicast frame

Question 3

A protocol that allows a switch to dynamically work around loops in a network topology by detecting loops and removing them by blocking selected switch interfaces

Answer 3

Spanning Tree Protocol

Question 4

An Ethernet frame whose destination MAC address is not listed in the switch’s MAC address-table, so the switch must flood the frame

Answer 4

unknown unicast frame

Question 5

A table of forwarding information held by a Layer 2 switch, built dynamically by listening to incoming frames and used by the switch to match frames to make forwarding decisions

Answer 5

MAC address table

Question 6

To send a frame received in one interface out another interface, toward its ultimate destination

Answer 6

forward/forwarding

Question 7

The result of the LAN switching forwarding process for broadcasts and unknown unicast frames. These frames are forwarded all interfaces, except for the interface on which the were received

Answer 7

flooding

Question 8

Command reference: Shows all MAC address table entries of all types

Answer 8

show mac address-table

Question 9

Command reference: Shows all dynamically learned MAC table entries

Answer 9

show mac address-table dynamic

Question 10

Command reference: Shows all dynamically learned MAC table entries in particular vlan

Answer 10

show mac address-table dynamic vlan vlan-id

Question 11

Command reference: Shows the dynamically learned MAC table entries with that particular MAC address

Answer 11

show mac address-table dynamic address mac-address

Question 12

Command reference: Shows all dynamically learned MAC table entries associated with a particular interface

Answer 12

show mac address-table dynamic interface interface-id

Question 13

Command reference: Shows the number of entries in the MAC table, and the total number of remaining empty slots in the MAC table

Answer 13

show mac address-table count

Question 14

Command reference: Shows the global and per-VLAN aging timeout for inactive MAC table entries

Answer 14

show mac address-table aging-time

Question 15

Command reference: Clears the MAC address table of all dynamic entries

Answer 15

clear mac address-table dynamic

Question 16

Command reference: Lists one line per interface on the switch, with basic status and operating information for each

Answer 16

show interfaces status

Question 17

Which command likely produced the following output?

Answer 17

show mac address-table dynamic

Question 18

Which command likely produced the following output?

Answer 18

show interfaces status

Question 19

Which command likely produced the following output:

Answer 19

show interfaces fa0/1 counters

Question 20

In the figure, the first command lists all dynamicly learned MAC addresses. What two possible commands could have resulted in the bottom output?

Answer 20

show mac address-table dynamic address 0200.1111.1111

show mac address-table dynamic interface fa0/1

Question 21

What command produced the following output:

Answer 21

show mac address-table aging-time

Question 22

What command produced the follwing output:

Answer 22

show mac address-table count

Question 23

What are the three main functions of a LAN switch?

Answer 23

1. Forward frames based on destination MAC address
2. Learn and fill the MAC address table by examining the source MAC address and port of incoming frames
3. Prevent switching loops via STP

Question 24

Describe the process of forwarding a known unicast frame.

Answer 24

1. Examine the destination MAC address
2. Compare destination MAC address to MAC address table and match the destination port
3. Forward the frame through the matched port
4. Filter the frame from all other ports

Question 25

Describe the switch’s process of learning MAC addresses

Answer 25

1. Examine source MAC address of incoming frame
2. Is MAC address in the address table?
3. If yes, reset the aging timer for that table entry
4. If no, add the MAC address and associated incoming port to the MAC address table

Question 26

Summarize a switch’s forwarding logic.

Answer 26

1. Forward frames based on destination port
   a. is destination broadcast or unknown unicast? if so, forward frame out all ports except incoming port
   b. Destination address is known unicast; match destination address to associated port in MAC address table, forward frame out the associated port only.
2. Learn MAC addresses
   a. For each incoming frame, examine source MAC address and note receiving port
   b. if not already in MAC address table, add entry for that address and port
3. Prevent loops using STP